def write_datafile(self): datafile = self.get_overlay_data_location() fh = open(datafile, "w") fh.write("year\tEfficiency\n") for i in range(len(self.xvalues)): x = self.xvalues[i] y = self.overlay_values[x] fh.write(str(x) + "\t" + str(y) + "\n") fh.close() GNUPlot.write_datafile(self)